Barnett J4B2

Chiefmole999

Junior Member
Joined
Oct 9, 2007
Messages
12
Location
Bath
Short coupled?

Short coupled?

<<Jerrie Barnett makes several models all of which seem to be somewhat shortcoupled. There have also been some prangs of the side-by-side BRC 540 (one that has been repaired after a low-speed crash is now being used by Piasecki for UAV gyro research and development).>>

Hognose posted the above, - I wonder if anyone could explain what "short coupled" means. What is the effect of this, and why is it a bad thing?

Cheers Cheifmole999
 

Hognose

Platinum Member
Joined
Nov 14, 2003
Messages
2,182
Location
Seacoast New Hampshire, USA
Aircraft
PA-28/J-3/various
Total Flight Time
Gyro - 2.5! FW, hundreds not thousands. Helo, 0 (some day!)
Philip,

Karl posted exactly what I meant -- the Barnett gyros all appear to have the tail very close to the cabin. In some gyroplanes the lateral (left-right) stability suffers because of too little tail force. The tail force can be increased by making the tail larger or putting it further back (increasing the moment arm). For an aircraft to be stable in any given axis, the centre of pressure should be behind the centre of mass.

This is strictly a theoretical concern. I have not flown any Barnett gyro. On the other thread CFI Chris Burgess mentioned that he had some time in the BRC 540 and asked you to PM him -- recommend you do that, if not already done. He will be able to give you an expert's opinion on the aircraft based on actual stick time.

A typical effect of a shortcoupled aircraft is that it "hunts" a bit left and right of the selected heading. In extreme cases, i.e. machine with much larger cabin than tail being skidded sideways, the result can be loss of control. One of the old-timers on the forum witnessed a gyro prang like that. (Chuck B?) Sideways flying was one cause of the plague of mast-bumping mishaps we had in UH1D and -H in the US Army. Much safer to do with doors open than with doors shut.

By the way, looking at the lines you cite from my post it looks like I was saying that BRC 540s are dropping like flies! Not the case. I believe there were two mishaps in the runway environment, neither fatal, one in NTSB and one not. There are about five J4B mishaps in the NTSB database, and most of them fall under "stupid pilot tricks". Two were fatal, one guy hit the towline between a towplane and a glider and the other was unlicensed, untrained, and threw a second-hand gyro together without a hang test and went flying.

I was mortified looking at that pull quote, it looks like I'm saying Jerrie builds unsafe machines! ZUG! Not what I was trying to say at all.

Finally, one more thing to think about up there in Bath -- you probably want to have a machine that other guys in Britain have. Then you have some reasonable prospect of networking locally with fellows in the same time zone and same regulatory environment.

Most of us find the idea of going it alone attractive, but there is safety in numbers.

cheers

-=K=-
 

Randy White

Newbie
Joined
Jun 1, 2022
Messages
1
Location
Tulsa, OK
the ntsb report relating to the loss of control describes one of the pilot control inputs as a "cyclic" reduction..... Must be a pretty uncommon autogyro to have a cyclic stick. I must be too new to the sport to recognize some of the terms employed in the industry. I am SEL, helicopter, and glider rated.....but im always willing to learn something new...........:)
The cyclic reduction they are referring to is the pulling back the stick, chopping the throttle. There incident was a low time gyro pilot. Over 2000 hours in fixed wings. High speed taxi, wind gust and ballooned 50 ft in the air. Rather than apply power and get control, the aircraft lost lift and had a hard landing and roll over. Pilot walked away. This was a j4b. One Jerry had built.
 
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